This invention relates to a method and apparatus for fastening mechanically screw means onto a metal plate, and a metal plate having screw means fastened thereonto.
In the mechanical industry it is required for certain application that a screw means, for instance, a screw or a bolt is secured onto a metal plate such as a base board or the like, or the head portion of the screw means is enlarged much wider than the screw body thereof. To meet the requirement, an invention disclosed in Japanese Utility Model Publication No. 20,536/1959, one of hitherto known technics proposes a method comprizing providing a screw with a stepped neck at the filet of the head thereof, inserting the stepped neck into an opening piercing a metal plate and applying caulking operation to the edge portion of the stepped neck of the screw so that it is secured onto the metal plate through the opening. It is pointed out with the above hitherto known method, however, that the fastening effect of the screw into the opening is unstable and insufficient merely with the "caulking operation" mentioned in the above known technics and moreover it is practically impossible to inspect on-site how tightly the screw is fastened.
Furthermore, a conventional welding method for fastening a plurality of screw means onto a metal plate brings the disadvantage that the plural screw means fastened onto the metal plate are apt to become irregular, that is, the axes of the screw means adjacent to each other are not in one plane and are not parallel to each other, because the fastened assembly of the screw means and the metal plate is deformed due to heat applied thereto in the welding operation. Such irregularity is undesirable since the plural screw means which have been fastened onto the metal plate cannot be engaged smoothly with an article to which the screw means are to be installed.